Control device



May 23, 1939. D Q TAYLQR 2,159,513

CONTROL DEvcE Filed Aug. 7, 1937 3 Sheets-Sheet l D. G. TAYLOR CONTROLDEVICE May 23, 1939 Filed Aug. '7, 1957 3 Sheets-Sheet 2 izq IZ 15a D.G. TAYLOR CONTROL DEVICE -May 23, 1939.

3 Sheets-Sheet 5 Filed Aug. 7, 1937 Jay. 11

J 4 e E H v y Patented May 23, 1939 PATENT OFFICE coN'raoL DEVICE DanielG. Taylor, Minneapolis, Minn., assignor to Minneapolis-HoneywellRegulator VCompany, Minneapolis, Minn., a. corporation of DelawareApplication August 7, 1937, Serial No. 157,933`

18 Claims.

This invention relates to control devices in general and moreparticularly to control devices of the type disclosed in Lewis L.Cunningham Patent 2,041,050 granted May 19, 1936.

l It is an object of this invention to `provide a new and novelmechanism for adjusting the differential of operation of a controldevice.

A further object is to provide a mechanism 'whereby the operatingdifferential may -be ad- 10 justed without disturbing the temperaturesetting of the device.

Another object is to provide a device which Will move an arm graduallyin accordance with a condition change and where the amount of movel5ment for a given change in the condition may be varied.

Another object is to provide a' mechanism wherein the range of conditionchange necessary to move the control device completely may be 20 variedby keeping the mid-point of the range constant and varying the upper andlower limits, or

by keeping the upper limit constant and varying the lower limit, or bykeeping `the lower limit constant and varying the upper limit.

Another object is to provide a mechanism wherein the range of conditionchange necessary to move the control device completely may be varied, atthe same time keeping any one point in the range constant and varyingthe limits.

Further objects will become apparent from the description and drawingsforming a part of this specification.

For a more thorough understanding of this inu vention reference is madeto the accompanying 35 drawings in which:

Figure 1 isan eleyational view of one form of this invention;

Figure 2 is a plan view looking down on Figure 1r .I Figure 3 is apartial sectional view looking 'to the right in Figure 1;

Figure 4 is a perspective view of a portion of the mechanism utilized inFigure l; f

Figure 5 is an elevational view' of another form .15 of this invention;

Figure 6 is a sectional view taken substantially along the liner Ii-- ofFigure 5;

Figure '7 isa fragmentary view taken substantially alongthe line 1-1 ofFigure 6;

Figure 8 is a fragmentary view taken substantially along the line `8 8of Figure 5;

Figure 9 is an elevational View of still another form of this invention;

Figure l0 is a fragmentary view taken substan- 5 tially along the lineIII-IllA of Figure i2;

(Cl. 'Z4-99) Figure 11 is a perspective view of a portion of themechanism included in Figure 9; and

Figure 12 is a perspective view of another portion of the mechanismcontained in Figure 9.

Referring now to Figures l to 4-inclusive, i0 designates a base platepreferably made of insulating material and having suitable electricalterminals II. A bracket I2 is secured to the base I0 as by means ofscrews I2' (Figure 3). This bracket I2 carries a stud I3 upon which aresuitably mounted resistance elements I4 and I5. Also secured to thebracket I2 is a stud I6 carrying nuts I1 and I8 which form limit stopsas will be pointed out more fully hereafter.

Secured to the base IIl is a bracket 20 upon which is mounted a bellows2l by means of a screw 22. The bellows 2l preferably contains a volatilefluid so that upon an increase in the temperature affecting bellows 2I,the bellows expands, and upon a decrease in temperature the bellowscontracts. A bracket 23 is secured to the base I0 and a rod 2l.extending between the brackets 20 and 23 brace and hold the variousparts in assembled relation. The bracket 23 carries a knife edge orfulcrum 25 upon which is pivotally mounted a lever 26. The bellows 2Icarries a plunger 21 which engages in a depression in the lever 26. Aknife edge arrangement 28 engages the lever 2E and is carried by a screw29 which, in turn, is secured by a nut 29 to one end of spring 3U. Theother end of the spring 30 is fastened to a nut 3l which is screwthreadedly mounted on a screw 32 having a head 33 which projects looselythrough a hole in the bracket I2. The nut 3l is provided with anextension 35 which slides in a slot 36 of a plate 31. The plate 31 isprovided with elongated slots 38 through which extend screws 39 foradjustably mounting the plate 31 to the bracket I2. The extension 35operating in the slot 36 prevents rotation of the nuil 3| so that byturning the screw 32 the nut 3l is moved upwardly or downwardly to varythe tension in the spring 30. The extension 35 alsocooperates withindicia carried by the plate 31 to indicate the tension in the spring3l). The screw 29 which carries the fulcrum member 28 provides a factorycalibration of this portion of the instrument. The instrument may befurther calibrated by longitudinally adjusting the scale plate 31. Thelever 26 is provided with an upwardly extending portion 4U locatedadjacent the stop nuts I1 and I8.

Upon an increase in temperature affecting the bellows 2| the plunger 21operates the lever 26 in a counterclockwise direction about the pivot 25against the action of the spring Sli. Upon a decrease in temperatureaffecting the bellows 2l the spring 38 rotates the lever 2t in aclockwise direction about the pivot 25. The stop nuts l l and l@limit-the amount of movement of the lever in either direction. Bysuitably adjusting the tension in the spring 30 the temperature settingof the instrument may be varied at will.

rlhe lever 2li carries a bracket d2 to which are secured resilientsliders i3 and id as by means o screws 45. Suitable insulating padselectrically insulate the sliders 4? and 44 from each other and from thebracket 42. The sliders i3 and Ml slidably engage the resistanceelements l@ and [l5 to provide adjustable rheostats or potentiometersdepending upon the manner in which these resistance elements and slidersare connected to the various terminals tl. 'llhe sliders 33 and irl aretherefore moved to the left with respect to the resistance elements il@and |15 upon a temperature rise and move to the right upon a temperaturefall.' 'lhe sliders and dd are therefore positioned directly inaccordance with the value of the .temperature affecting the bellows 2l.

An extending portion W is struck out from the lever 2G and one end or alink 48 engages this portion il The other end of the link d8 engages alever d@ which is pivoted upon a pin titl. One end of a spring 5l isconnected to the lever lil and the other end thereof is connected to anut 52 which is screw threadedly mounted on a screw 58 having a head 54inserted loosely through a hole in the bracket i2. The nut 52 isprovided with a bifurcated extension 55 slidably engaging a scale plate58. The scale plate 56 is provided with slots 5l through which extendscrews 58 for slidably mounting the scale plate 5t on the bracket l2.The bifurcated extension 55 prevents rotation of the nut 52 andtherefore rotation of the screw 53 increases or decreases the tensionwith the spring 5|. The amount of tension in the spring 5i is indicatedby the extension 55 and the indicia carried by the plate 56. The plate56 may be longitudinally adjusted for calibration purposes.

The pivot pin 50 for the lever 49 is carried by an arm 6| pivoted at 62to the bracket i2. The

arm 6| is provided with a slot 62' through which extends a screw 63 foradjustably holding the arm 6| in any of its rotatably adjustedpositions. The spring 5| is adapted under certain circumstances, to addresistance to the movement of the bellows 2|. f g

With the parts in the position shown in Figure 1 the extension 40 oflever 26 is midway between the stop nuts |1 and I8, the sliders 43 and44 are spaced midway along the resistance elements |4 and l5, the screw63 is midway of the slot 62 and the link 48 is in line with the fulcrumpoint 25 as shown by the dot and dash line A in Figure 1. Since the twocontact points of link 48 with lever 43 and struck out portion 41 oflever 26 are directly in line with the pivot point 25 of lever 26, anyvariation of the pull exerted by link 48 on lever 26 can have no effectupon its position. 'I'his is because the force is exerted directly inline with the pivot and hence there is no lever arm to cause a turningmovement. If, however, the lever26 is moved in a counter-clockwisedirection upon expansion of the bellows 2| the link 48 is moved in aclockwise direction out of line with the fulcrum 25. This clockwisemovement of the link 48 produces the effective moment arm or leverage.arm formed thereby so that the spring 5| increasingly retards movementof the lever 26.

aisasis rTherefore more eort must be expended by the bellows 2l to movethe lever t@ a predetermined distance in a counter-clockwise directionthan if the link #i8 and the spring 5l were not present.. Since theeffective moment arm which transmits the retarding effect of the spring5l increases from zero in the position shown in Figure i. at asubstantially constant rate as the lever 2G is rotated in acounter-clockwise direction, the amount of retarding force of theVspring 5l is increased at a substantially constant rate.

In a like manner contraction ci the bellows 2li as a result of adecrease "in temperature causes the spring 3U to move the lever 2li in aclockwise direction and'this clockwise movement of lever 2li from theposition shown in Figure l is retarded by the increasing moment armafforded by the counter-clockwise rotation of the link liti. The amountof retarding effect of the spring 5l increases approximately inproportion to the amount or" clockwise rotation of the lever 26 from theposition shown in Figure l.

From the above it is seenthat with the parts in the position shown inFigure l the spring di has substantially no effect upon the movement ofthe lever E@ since the link [lil aligns 'with fulcrum 25, but as thelink 48 is moved out of alignment with the fulcrum in either direction,the spring 5l increasingly retards movement of the lever 2li. rlheamount of retarding may be varied by suitably adjusting the tension inthe spring 5l. If there be very little tension in the spring a 1temperature change may cause cornplete movement of the sliders i3 and 44across the resistance elements i4 and l5, but if the tension in thespring 5l is increased the amount of ternperature change required tomove the sliders 43 and 44 completely across the resistance elementslill and [I5 is correspondingly increased. It follows then that byadjusting the spring 5l the differential of the control instrument isvaried independently of the temperature setting of the instrument whichis controlled by the adjustment of the springE 30. Therefore thetemperature setting of .the instrument and the differential setting maybe independently adjusted at will. gardless of the differential settingthe sliders 43 and 44 will assume a mid position with respect to the.resistance elements |4 and l5 when the temperature assumes a givenvalue. In other Words, when the temperature aiecting the bellows 2|, issay, 70 the sliders 43 and 44 will be in a mid position regardless ofthe tension in the spring 5| since the spring 5| has no eiect when thesliders are in this position. By adjusting the differential of theinstrument both ends of the range are varied while the mid point of therange is maintained constant.

The above mode of operation is predicated on the lever 6| being adjustedin the mid position as shown in Figure 1. If, however, the lever 6| isadjusted downwardly so that the screw 63 engages the upper end of theslot 62 the pivot point 50 for the lever 49 is shifted to the left whichcauses counter-clockwise rotation of the link 48, The link 48 isthereupon moved out of alignment with the fulcrum 25 and in order toalign the link 48 with the fulcrum 25 the sliders 43 and 44 must bemoved to the left. With this adjustment therefore the link 48 is inalignment with the fulcrum 45 when the sliders 43 and 44 are in theextreme left-hand position. At this position of the sliders 43 and 44the spring 5| has no eiect by reason of the alignment of link 48 betweenthe fulcrum 45. When, however, the sliders 43 and 44 are moved to theright with respect to the resistance elements I4 and I5, the spring 5|immediately becomes operative to retard this movement and the amount ofretarding eect increases as the sliders 43 and 44 are moved to theright. Therefore, with thegparts adjusted in this manner a tightening ofthe spring 5| increases the differential but the left hand portion ofthe range of movement is maintained constant regardless'of thedifferential adjustment. In other words the left-hand end of the rangeof movementof the sliders 43 and ,44 remains constant while theright-hand range of movement is varied.

Assume now that the arm 6| is adjusted upwardly so that the screw 63engages the lower end of the slot 62, the pivot pin 50 is moved to theright and under these circumstances the link 48 aligns with the fulcrum45 only when the sliders 43-and 44 are in the extreme right-handposition. By adjusting the differential spring 5| with the arm 6| inthis position the right hand end of the range of movement remainsconstant while the left-hand end -is varied. I

From the above it is seen that theregis provided a temperatureresponsive instrument wherein means are provided for adjusting thetemperature setting thereof, wherein means are provided forindependently adjusting the diierentlal of operation of the instrumentand wherein means are also provided for maintaining the mid point of ther-ange constant, one end point of the range constant or the otherendpoint of the range constant or any given point within the range may bemaintained constant regardless of the differential adjustment.

Referring to the second 'modification as disclosed in Figures 5 to 8,||0 designates a cup shaped casing which contains the control device.Attached to the bottonr of this casing 'as by screws- III is a bellowshousing H2. B/racket ||3 which is attached tothe back of casing I0 byscrews I I4 has an upstanding arm ||5 having at its end a knife edge IIBwhich seats in a dwell in lever ||1. Lever ||1 has a bearing member ||8against which bears pin Il! which is connected to a bellows memberwithin housing II2. Connected to the right-hand end of lever ||1,looking at Figure 5, is a supporting member on which is mounted aU-shaped bracket |2| having twolegs |22 and |23 located one directlybehind the other as viewed in Figure 5, each of which carries a flexiblearm |24 which in turn carries a sliding contact member |25. Each ofthese sliding contact members engages a potentiometer |2|il alsolocatedone directly behind the other as viewed in Figure' V5. 'I'hesepotentiometers are supported on an upstanding arm |21 of a bracketmember |23 which is adjustably secured to casing ||0 by means of screws|29 and slots |30. Also attached to casing 0 is a U- shaped bracket |3|having two legs |32 and |33 which act as stops for lever member ||1limiting its movementin either direction.

As the bellows member expands it swings lever ||1 in a counter-clockwisedirection which moves the sliding contacts `|25 to the left as viewed inFigure 5. Conversely, as the bellows member contracts fthe slidingcontacts are moved towards the right in a manner to be disclosed. Spring|34 is supported by a nut |35 which inturn is screw threadedly attachedto a screw which extends loosely through a hole in casing ||0. The loweren'd of spring |34 carriesa depending member which supports a knife edge|31 Dwhich entension of spring |45.

gages underneath leverul I1. The function of this spring is to tend torotate lever I1 in a clockwise direction about its pivot IIB inopposition to the force exerted on it by the bellows. Rigidly attachedto nut |35 is an arm |30 which "has an end |39 which projects through aslot-in casing ||0. As screw |36 is rotated this arm |38 will preventthe rotation of nut |35 which will move either up or down depending uponthe direction of rotation of screw |36. Adjustment of this spring |34 inthis manner will adjust the position of contact |25 with respect to agiven value of the condition to which the bellows responds, Thusassuming that the bellows responds to temperature changes, thetemperature setting of the device will be varied by changing the tensionof y spring |34. Bracket |40 has an upstanding arm |4| upon which ispivoted a lever |42 to the other end of which is pivoted a second lever|43 as at |44. To this lever is attached a second spring member |45whose upper end is attached to a nut |46. This nut is screw threadedlyattached to a screw |41 which depends loosely through a hole in casingI0. Also rigidly attached to this nut is an arm |48 which has one end|43 which extends through a' slot in the casing ||0. This arm |43prevents the rotation of nut |45 when screw |41 is rotated and thereforeas yscrew |41 is rotated.

this -nut |46 will `move up or down to adjust the Lever ||1 has attachedthereto a hooked member |50. A link |5| is engaged under this hookedmember and also in a V slot in lever |42, thereby connecting them. Lever|43 is rotatably adjustable with respect to lever |42 by means of ascrew and slot connection |52, which adjustment is intended to be madeat the factory to initially set the device.

Assuming the parts to be in the4 position as' moving the contactn pointbetween link |5| and member |50"out of alignment with the other two.Spring |45 now exerts a force in opposition to this movement of thebellows which force gradually increases as the bellows continues to'movein this direction. 'Ihe tension of spring |45 being 1adjustable, thedifferential of the device or the `a counter-clockwise direction, at thesame time unit of movement per degree change of condition can be variedwithout, in this case, varying the lower limit of the Vrange in whichthe parts are shown in Figure 5. If, for example, it were desired thatthe4 center of the range were the one to remain fixed while thedifferential adjustment were made it would``be necessary to slidebracket |40 fto the left by means of the screw and slot connection |53to casing H0. This would move the contact' point of link |5| with thelever |42 to the left sothat the bellows would have to assume its midposition before the contact points of link |5| with lever |42 and member|50 and pivot point I6 oflever I |1 would be in alignment. Now if inthis position spring |45 were adjusted it would have no turning effecton lever ||1 because again there would be no n would move to the lettand the spring Hlt would enert a constantly increasing enect oncontinued movement. Again, ii the bellows were to lower pin` it springi3d would rotate lever llll'l in a clockwise direction and the contactpoint between link iti and member l5@ would move to the right and springM5 would exert a constantly increasing opposing effect. in the same waythe device could be adjusted so that the upper range could remain fixedas the difierential setting is adjusted.

The potentiometer i2@ is connected by wires and 05d to terminals 055 andl5@ and the siiding contact carrier arm 02d is connected to terminaltbl, which terminals in turn are connected to outside control circuitsin a well known manner.

`Referring now to the third modification which is disclosed in Figures 9to l2 inclusive, reference numeral 2i@ designates a cup-shaped casingwhich contains the control device. Attached to the bottoni of thiscasing is a housing 2M for a bellows which acts as a sensitive devicefor operating the control device, this bellows being connected by meansof a tubing 2G22 to respond to a condition to be controlled. Bracket 2t@is attached to the baci; of the casing El@ and has a iorwardly extendingarm 2id at the bottom edge of which are two downwardly directed knifeedges (see Tligure ld) for a purpose to be hereinafter disclosed. Spring2i@ is rigidly connected at its top to a nut lllll which is screwthreadedly attached to a screw 2i@ which loosely extends through a holein housing 2i mounted on top oi casing 2id. Alned to nut dil! is an arm22@ which projects outwardly through a slot in the side ci casing 2 l@thus preventing rotation oi nut 2W when screw 2i@ is rotated. Thereforeupon rotation or screw 2l@ nut 2li( will move in a vertical line andthus raise and lower the top oi the spring El@ and adjust its tension.Fastened to the outside or casing 2l@ is a plate bearing indicia forcooperation with the end of arno. 22@ to indicate the position of nut2i?! and therefore the tension or spring This plateis covered by meansof a transparent material such as Celluloid and is adjustably securedtothe casing 2l@ by means of slot and screw connections 22 i. EX-tending irom the bottom of spring fil@ ls a support or carriage for anupwardly directed knife edge Cooperat g with the three knife edgesdescribed is a lever member 223 having two vshaped dwells 226 therein inwhich are seated the two knife edges 2lb and which form a pivot for thislever. The lever also contains another V.- shaped dwell in which isseated the knife edge 222g The 'tension spring Zit through its knifeedge 222 tends to rotate this lever in a clockwise direction, but suchrotation is lopposed by a pin 22d seated in bearing member 2271 of lever223,

'which pin is connected to the bellows member.

The raising of pin 22@ by the bellows will thereiore causecounter-clockwise rotation of the lever in opposition to the action cithe spring Zit'and lowering of pin di@ by the bellows will permit spring2lb to. rotate the leverv in a clockwise clirectlon. Mounted /onthebackof casing 2lb is a bracket 228 having two spaced arms 229 which actas stops for the lever 223. Mounted on the right-handiend of this leveris a U-shaped member 230 upon each leg of which is mounted a resilientarm 23| carrying a sliding contact member ft2. Only one arm and contactare visible due to the fact that one is directly behind the otheras-Viewed in Figure 9. Bracket 233 is adjustably aisasis mounted on theback of the casing member 2m and carries two potentiometers orresistances i231! on an upstanding arm thereof The sliding contactmembers are arranged to cooperate with these potentiometers.

The apparatus thus far described is a condi tion responsive device forvariably operating a pair of potentiometers, said device beingadjustable by means of screw 2l@ which varies the tension of spring 2l@acting against the bellows. There will now be described a mechanism forvarying the dierential of the device. This inech-= anism comprises abracket which is iiireolly mounted on the left-hand side of lever Plv--otally mounted on this bracket is a member Ztl having an arcuate slot2238 formed about the pivot as a center. Screw threaded in the bracket236 is a screw 2li@ which also slidingly engages in the slot 238.Rotation oi this screw in the proper direction will clamp bracket 236and member 233i together. kR;otatably mounted in bracket is a pin memberwhose .head lll is eccentrically mount/ed with respect to its stern 2&2.Head Qdi is loosely contained. in a slot in member 23W the width oiwhich slotv is the same size as the diameter of the head. the relativepositions oi the bracket and ineinber 237 it is necessary only to loosenscrew ldil and rotate pin member 25H which acts as a cam in rotatingmember 237i about its pivot liter the proper relative position has beenobtained the members may again be clamped tightly by tightening screwRlgidly attached to the side o ,casing 2li@ is a bracket 2135 having twoarms 2d@ between which is pivoted a generally U-shaped member itl, onearm of which is connected with spring 2id. The upper end of this springis attached to nut member 2d@ which is in turn screw threadedlyconnected with a screw 25@ loosely extending through a hole in the topof casing 2id. Plate iol is adjustably carried by bracket 252 by meansof screws in slot 254. An arm 25W which is rigidly attached to nut 2tlgrides in a slot 25d in plate i259, thus preventlng rotation of the nutas screw 25d is rotated. This permits the upper end ci spring Mil to bevertically adjusted by rotation oi screw 25d, the

adjustment being indicated by indicia 'inscribed on plate 250. MembersZtl and 2M are each provided with hooked arms which cooperate with f alink itil and are held together thereby.

As in the previous modications when the contact points between link il'land members Ml and iil and the pivot point of lever 2% are in a,straight line, adjustment oil the tension of spring tilt can have norotating effect on the lever. This condition prevails with the parts inthe position shown in Figure 9 which is in this instance the topmostpoint of the control range. Upon downward movement of pin 226 levez` 223will swing in a clockwise direction which will move the contact pointbetween link itil and member 3l to the right and out of line with theother two points. Now spring MB will have an effect upon .the rotationof lever 223 and will tend to retard this movement. As in the other twomodifications, the amount of this effect, or the differential of thedevice, can be varied by adjusting the tension o! spring 248. Assume forexample that the devise is arranged to respond to temperature and lthatthe lower range of temperature desired is 68 F. and the upper limitdesired is 72; that is, a differential of i, With the parts in theposition shown, it is necessary only to adjust the tension of spring Toadjust l ill 2li so that at '12 the slider contact is at the extremeleftas shown. Now spring 248 is adjusted until a 4 fall in temperature isjust sufficient to swing `the slider contact 232 to the right side ofthe potentiometer.

The device is adjusted in Figure 9 so that the contact points betweenlink 251 and hooked arms 241 and 231iare aligned4 with the .pivot point2|5 for lever 223 when the slider contact 232 is at the topmokst pointin the range. This means that the differential setting may be variedwithout varying the upper temperature limit. Thus assuming the limitsare now 68 and 72, if spring.

243 were loosened the lower limit would be raised and the upper limitwould n remain at '12". If spring 243 were tightened, the `lower limitwould be 'Icecreased and the upper limit would remain at As in the othertwo modifications, the devicc may be adjusted so that any point in therange may be made to remain constant as the differential settng isadjusted. This Yis accomplished by rotating member 231 with respect tobracket 236 as described, thus moving the contact point of link 251 withmember 231. In this manner the contact points of link 251 with members236 and 231 and the pivot 2I5 of lever 223 can be placed in alignment atany point in the range of the device.

It is to be understood that the above disclosure is intended to beillustrative only and that various modifications within the scope ofthis invention will occur to those skilled in the art. Therefore theinvention is to be limited only by the scope of the appended'claims.

I claim:

1. In a mechanim of the character described, a pivoted lever, anadjustable spring member constantly tending to .rotate said lever in onedirection, a condition responsive member tending to rotate the lever inthe opposite direction, a second lever, a tension link connecting saidtwo levers and preventing separation thereof, an adjustable tensionspring nornally tending to cause movement of saidsecond lever away fromsaid first lever and thereby causing movement of said first lever in adirection to oppose the action of vsaid condition responsive member, thearrangement Ibeing such that when the contact points of said link withsaid two levers are aligned with the pivot point of said first leversaid tension spring has no rotative effect on said first lever, but asthe condition responsive element rotates said first lever out of theabove mentioned position'said second spring increasingly resists saidmotion,

2. In a mechanism of the character described, a pivoted lever, anadjustable spring member constantly tending to rotate said lever in onedirection, a condition responsive member tending to rotate the lever inthe opposite direction, a second lever, a link connecting said twolevers, a second adjustable spring normally tending to cause rotation ofsaid second lever, the arrange- A ment being such that when the contactpoints lof said link-with said two Lleversare aligned with the pivotpoint of said first lever said second spring has no rotative eii'ect onsaid dirst lever, but when the condition responsive element rotates saidfrsJt lever out of the above mentioned position said second springincreasingly resists said motion, and means for varying the position ofthe iirst lever at which its pivot is aligned with the twoaforementioned contact points.

a mechanism of the character described,

a pivoted lever, an adjustable spring member constantly tending torotate said lever in one direction, a condition responsive membertending to rotate the lever in the opposite direction, a second lever, alink connecting said two levers, a second adjustable spring normallytending to cause rotation of said second lever, the ari-angement beingsuch that when the contact points of said link with said two levers arealigned with the pivot point of said first lever said second spring hasno rotative effect on said first lever, but when the conditionresponsive element rotates said rst lever out of the above mentionedposition said second spring increasingly` resists said motion, and meansfor varying the position of the first lever at which its pivot isaligned with the two aforementioned contact points, said meanscomprising an adjustment for the support' of said second lever.

4. Ian a mechanism of the character described, a pivoted lever, anadjustable springmember constantly tending to rotate said lever in onedirection, a condition responsive member tending t0 rotate the lever inthe opposite direction, a second lever, a link connecting said twolevers, a second adjustable spring normally tending to cause rotation ofsaid second lever, the arrangement being such that when the contactpoints of said link with said `two levers are aligned with the pivotpoint of said first lever said second spring has no rotative effect onsaid first lever, but when the condition responsive element rotates saidfirst lever out of the above mentioned position said second springincreasingly resists said motion, and means for varying the position .ofthe first lever at which its pivot is aligned with the twoaforementioned contact points, said means comprising a rotativeadjustment for the support of said second lever.

5. In a mechanism of the character described, a pivoted lever,`anadjustable spring member constantly tending to rotate said lever in onedirection, a condition responsive member tending to rotate the lever inthe opposite direction, a second lever, a link connecting said twolevers, aI second adjustable spring normally tending to cause rotationof said second lever, the arrangement being such that' when the contactpoints of said link with said two levers are aligned with the pivotpoint of said first lever said second spring has f' no rotative effecton said first lever, but when the condition responsive element rotatessaid first lever out of the above mentioned position said second springincreasingly resists said motion, and means for varying the( position ofthe first lever at which its pivot is aligned with the twoaforementioned contact points, said means comprising a slidingadjustment forthe support of said second lever.

6. In a mechanism of the character described, a pivoted lever, anadjustable spring member constantly tending to rotate said lever in onedirection, a condition responsive member tending to rotate the lever inthe oppositev direction, a second lever, ai link connecting said twolevers, a second adjustable spring normally tending` to cause rotationof said second lever, the arrangement being such that when the contactpoints of said link with said two levers are aligned with` the pivotpoint of said first lever said second spring has noy rotative eifect onsaid first lever, but when the condition responsive element rosaidmotion, and means for varying the position l co ,of the nrst lever atwhich its pivot is with the two aforementioned contact points, saidmeans comprising a memberadiustably con= nected to one of said leversfor varying the coned tact point between said lever and said l. ln amechanism of the character described, lever pivoted'at a pointintermediate two ends, an adjustably tensioned spring connected to saidlever on one side of said pivot and holding a point on the other side ofsaid pivot against a bellows member, a second lever, a screw looselyprojecting downwardly through a hole in a fined support, a nut threadedon said screw, said nut being held against rotation, a second spring oneend oi which is connected to said nut and the other connected to saidsecond lever, a link con1 nectmg said levers, the contact points of slink with said levers being aligned with the pivot point of said lrstlever in one position thereo, at which time said second spring has noelect upon said nrst lever, said second spring increase ingly resistingmovement by said bellows ine her of said nrst lever out of said positionin en, W c rection, and ,means for varying the posit which the contactpoints ci said linls with ss levers are aligned with the pivot point orfirst lever. ln a mechanism of the character a pivoted lever, anadjustable spring mh constantly tending to rotate said lever direction,a bellows tending to rotate the lever in the opposite direction, meansior limiting the travel oi said lever in each direction, 'a secondlever, a tension linl: connecting said two levers and preventingseparation thereof, an adlustable tension spring normally tending tocanse rotsetic-n ci said second lever and through the me ir2 or saidlink, of said first lever in a direction opposing the action of saidbellows, the ment being such that when the contact points ci said linlr.with said two levers are aligned with the pivot point of said i'lrstlever said tension spring has no rotative effect on said lever, lontwhen the bellows rotates said lrst lever ont or the above mentionedposition said second spring increasingly resists said motion,

' t. ln a control device of the type having, a

resistance element and a resilient contact arm for slidingly engagingsaid element, the improvc= ment which comprises a pivoted lever for con=trolling the position of said contact arm, an ad= Linstable springmember constantly tending to ro= tate said lever in one direction, abellows tending to rota the lever in the opposite direction, means forlimiting the travel of said lever in each direction, a second lever, alinl; connecting two levers, a second adjustable spring normally tendingto cause rotation oi said second lever, the arrangement being such thatwhen the con= tact points of said link with said two levers are alignedwith/ the pvot point of said rst lever said second spring has norotativeedect on said rlrst lever but when the bellows rotates saidmst lever outof thev above mentioned position said second spring increasingly resistssaid motion, and means for determining the position that said ilrstlever assumes when the contact points of i said link with said twolevers are aligned with the pivot point of said rst lever.

l0. ln combination, a casing, a control mechanism housed within saidcasing comprising a plvoted lever, a condition sensitive device tendingto rotate 'the lever in one direction, spring means tending to rotatethe lever in the opposite direc-s tion, adjusting means for said springcomprising i, for adjusting the tension of said second spring,

aioasia a screw loosely projecting through a hole in the top of saidcasing, a nut threaded to said screw, an arm rigidly connected to saidnut at one end and having its other end projecting through a slot insaid casing and cooperating with indicia 5 thereon, said spring beingattached to said nut, a second lever, a link connecting said two levers,a second adjustable spring normally tending to cause rotation of saidsecond lever, the arrangement being such that when the contact points oisaid linl; with said two levers are aligned with pivot point of saidfirst lever said second spring has no rotative effect on said rst lever,'ont when the condition responsive element rotates said iirst lever outof the above mentioned posim 1 tion said second spring. increasinglyresists said motion, and means for adjusting the location said abovementioned position.

ll. ln a mechanism of the character described, a control means, acondition sensitive device i L operating said control means, springmeans con--A stantly under tension r exerting a force on control means,means i'or preventing the exerted by said i substantial effect upon saidcontrol means one predetermined position "'l ereo, means varying theposition for whi t; force resisting any movement of said means out ofsaid predet ed position.

l2. l'n a mechanism ol the character described, n a control means, acondition sensitive device :lor operating said control means, sn ring'means con stantly under tension for exerting a force on said controlmeans, ineans jor preventing the force exerted by said spring means fromsubstantial effect upon said control i l one predeterini positionthereof, means 'or varying the posi ion for which this holds true, saidforce resisting any movement ci said con(- trol means out or saidpredetermined position, and ineans for adjusting the amount oi the iorceexerted by said spring means.

i3. ln a control device, a adapted 'to move in response to conditionchanges, a lever actuated thereby, a ulcruin for said lever, a springarranged to exert a pull on said lever in a direct line with saidnlcruin. when said lever is in one position, and to resistY the movementof said leverfrom` said position in proportion to the extentrof itsdeparture therefrom and means 5o for adjusting said one position to anypoint withu in the range o the control device.

lt. lrna control device, a member adapted to move in response tocondition changes, a lever actuated thereby, a fulcrnm for said lever, 5spring arranged to exert a pnll on said lever in a direct line with saidfulcrum when lever is in one position, and to resist the movement oisaid lever from `said position in proportion to the extent of itsdeparturethereirom, means ior adjusting the rate at which the springresists the movementof said lever, and v,means for adjust ing said oneposition to any'point within the Irange of the control device.

15. In a mechanism of the character described, a pivoted lever, a springconstantly tending to rotate said lever in one direction, a conditionresponsive member for rotating the lever in the opposite direction, asecond spring arranged to exert a pull on said lever in a direct linewith its pivot when said lever is in one position at which time saidsecond spring has la minimum length, k#rotation of said lever in eitherdirection causing elongaton of said second spring, separate means Cil onl nl maar..

and means for adjusting said one position to any point within the rangeof said mechanism.

16. In a mechanism of the character described, a pivoted lever, anadjustable spring member constantly tending to rotate said lever in onedirection, a bellows tending to .rotate the lever in the oppositedirection, means for limiting the travel of said lever in eachdirection, a second lever, a tension link connecting said two levers andpreventing separation thereof, an adjustable tension spring normallytending to cause rotation of said second lever and through t'he mediumof said link, of said first lever in a direction opposing the action ofsaid bellows, the arrangement being such that when the contact points ofsaid link with said two levers are aligned with the pivot point of saidrst lever said tension spring has no rotative effect on said rst lever,but when the bellows rotates said first lever out of the above mentionedposition said second spring increasingly resists said motion, and meansfor ad justing the position that said first lever assumes when thecontact points of said link with said two levers are aligned with thepivot point of said rst lever.

17. In a control device of the type having a resistance element and aresilient contact arm for slidingly engaging said element, theimprovement which comprises a pivoted lever for controlling the positionof said contact arm, an adjustable spring member constantly tending torotate said lever in one direction, a bellows tending to rotate thelever in the opposite direction, means i'or limiting the travel of saidlever in each direction, a second lever, a link connecting said twolevers, a second adjustable spring normally tending to cause rotation ofsaid second lever, the arrangement being such that when the contactpoints of said link with said two, levers are aligned with the pivotpoint of said iirst lever said second spring has no rotative effect onsaid first lever but when the bellows rotates said first lever out ofthe above mentioned position said second spring increasingly resistssaid motion, and means for determining the position that said iirstlever assumes when the contact points of said link with said two leversare aligned with the pivot point of said rst lever, said meanscomprising a member adjustably connected to said firstl lever forvarying the contact point between said first lever and said link.

18. In a mechanism of the character described, a pivoted lever arrangedto be moved in opposite directions from a neutral intermediate position,condition responsive means for imparting movement to said lever in onedirection, means biasing said lever in the opposite direction, a secondbiasing means, means connecting said second biasing means to said leverso that it hasno effect thereon when said lever is in said neutralintermediate position, so that it aids the biasing effect of said firstbiasing means with a gradually increasing force as said lever is movedfrom said neutral position in one directionand so that it opposes thebiasing effect of said rst biasing means with a gradually increasingforce as said lever is moved from said neutral position in said otherdirection, means varying the effect of said first biasing means so thatthe value of the condition required to move the lever to the neutralintermediate position may be varied, means varying the effect of saidsecond biasing means so that the distance the lever is moved from saidintermediate neutral position for a given change in the value of thecondition may be varied, and means for adjusting the position of thelever when it is in its neutral intermediate position. DANEL G. TAYLOR.

